Question

Why do all sugars except sucrose react with Benedict's reagent? Describe the sucrose molecule. What two sugars are bound together and what is the glycosidic bond?

Answer 1

All sugars react with Benedict's reagent except sucrose. It is because, except sucrose, other sugars have a reducing aldehyde moiety which will react with Benedict's reagent.

Sucrose contains two sugars glucose and fructose linked by glycosidic linkage. It doesn't have any reducing aldehyde.

In sucrose, glucose and fructose are linked through an ether bond between C-1 on the glucosyl subunit and C-2 on the fructosyl unit. This bond is called a glycosidic linkage.